1. Field
The present invention relates to communications systems. Specifically, the present invention relates to methods and apparatus for congestion control in a wireless communication system.
2. Background
In a wireless communication system, a base station communicates with multiple mobile users. Wireless communications may include low delay data communications, such as voice or video transmissions, or high data rate communications, such as packetized data transmissions. U.S. patent application No. 08/963,386, entitled “METHOD AND APPARATUS FOR HIGH RATE PACKET DATA TRANSMISSION,” filed Nov. 3, 1997 describes high rate packet data transmissions, and hereby expressly incorporated by reference.
In a wireless communication system, and specifically a system adapted for packetized transmissions, congestion and overloading may reduce the throughput of the system. Congestion is a measure of the amount of pending and active traffic with respect to the rated capacity of the system. System overload occurs when the pending and active traffic exceeds the rated capacity. A system may implement a target congestion level to maintain traffic conditions without interruption, i.e., to avoid overloading and underloading of resources.
One problem with overloading is the delayed transmission responses. An increase in response time often leads to application level timeouts, wherein an application requiring the data waits longer than the application is programmed to allow. Applications will then needlessly resend messages on timeouts, causing further congestion. If this condition continues, the system might reach a condition where it can service no users. Thus, in absence of any congestion control, the system will perform much below its rated capacity. There is a need therefore for congestion control that increases the efficiency of a wireless system and reduces the probability of overloading or a fault.